import {Component}from "react"
class DemoA extends Component{
    constructor(){
        super();//调用父组件的constructor
        console.log("constructor...");
    }
    componentDidMount(){
        console.log("componentDidMount..");
    }
    render(){
        console.log("render..",this)
        return( <h1>类组件</h1> )
    }
}
export default DemoA